Obamacare makes many significant changes to the U.S. health-care system, but one category of change stands out above all others: the degree to which the law reshapes the market for individually-purchased health insurance. Will the “Affordable Care Act” live up to its name and make health insurance less expensive? To help the public understand the impact of Obamacare on individual-market premiums, my Manhattan Institute colleagues and I have crunched the numbers and created an interactive, state-by-state map, where you can find out how Obamacare affects insurance rates where you live. The results may surprise you.

The relevant Obamacare insurance filings are still unavailable in 37 states

In less than four weeks—on October 1, 2013—Obamacares subsidized insurance exchanges are supposed to be fully on-line. But as of today, the relevant governmental agencies have only made public the insurance carrier filings for 13 states and the District of Columbia. In other words, were still waiting for important information on health insurance premiums from nearly three-fourths of the states.

As of September 4, the bulk of the data we have is from the subset of Democratic-leaning states that decided to set up their own insurance exchanges, instead of letting the federal government do so on their behalf.

(Of the 13 states plus D.C. for which we have the required data, all but one—South Dakota—voted for President Obama in the 2012 election. States whose rate changes you can now check on our Rate Map include: California, Colorado, Connecticut, D.C., Maine, New Mexico, New York, Ohio, Oregon, Rhode Island, the aforementioned South Dakota, Vermont, Virginia, and Washington state.)

We will be adding information to the map from the remaining states as they come on-line; Congressional sources inform me that Health and Human Services Secretary Kathleen Sebelius intends to release the data for the states participating in the federal exchange on September 19.

Most states are seeing rate hikes; some will see reductions

While these mostly-blue states will see an average premium increase of 24 percent, the impact of Obamacare is highly variable. Nine of the states will see increases on average, and five will see decreases on average. New Mexico, Vermont, South Dakota, and Connecticut will see the steepest rate hikes: on average, 130, 97, 83, and 59 percent, respectively. Four states will see meaningful declines in rates: Maine (71 percent), Colorado (34 percent), Ohio (30 percent), and New York (27 percent).

A number of blue states have heavily-regulated individual insurance markets that, in the recent past, have driven healthy people out of the market. Kentucky, Maine, Massachusetts, New Hampshire, New Jersey, New York, Vermont, and Washington have all experimented with Obamacare-like regulations, such as community rating (forcing young people to subsidize the old) and guaranteed issue (requiring insurers to offer plans regardless of pre-existing conditions).

Because Obamacare forces most Americans to buy health insurance, and subsidizes the purchase of that insurance for certain low-income populations, individual-market premiums in many of these highly-regulated states will go down. But in most others, rates will go up. If you want to know the details for a particular state, just click on the “State Rates” tab at the top, and then select the state youre interested in.

Who qualifies for Obamacares insurance subsidies?

When I first started writing about Obamacares impact on health insurance premiums, supporters of the law argued that premium hikes werent that important, because many poor people will be protected by taxpayer-funded subsidies. While subsidies are good news for the individuals who will receive them, most others will face a double whammy: higher premiums, and higher taxes to pay for those subsidies that others will receive.